致命错误：在非对象上调用成员函数format（）

Question

I've been reading every related question on SO, but I still don't understand where my error is.

On my wordpress site I have posts with a date that I need to display and I use this code:

$date = DateTime::createFromFormat('Ymd', '20071005');
/*error here*/ $year = $date->format('Y');
echo $year;

The information are displayed correctly and my code seems to me coherently object-oriented style. Yet I can't get rid of this message:

Fatal error: Call to a member function format() on a non-object in 
/homez.763/frommeto/www/temp/wp-content/themes/fmty/page-listspace.php on line 23

Can you see if there's anything really wrong? Might it be something related to the version of php the server is running? I'm using PHP 5.4.1

EDIT

var_dump($date) returns

object(DateTime)#84 (3) {
  ["date"]=>
  string(19) "2007-10-05 10:44:57"
  ["timezone_type"]=>
  int(3)
  ["timezone"]=>
  string(3) "UTC"
}

Answer 1

I copied and pasted your code and it worked just fine. I am using php5.4.11.

If all you are doing is trying to display the year, as in your example, you could use the strtotime() and date()

$date = strtotime('20071005') ;
$year = date('Y', $date) ; 

Or, more succinctly:

$year = date('Y',strtotime('20071005')) ;